Vocelli has it exactly right. This is a standard tactic when fishing for American shad in the Delaware river. You need light leaders because shad are extremely leader shy but they fight HARD. Newbys often break them off until someone clues them in to this technique. Side pressure works because just when the fish thinks he's winning you change the game on him, gain line and he's now got to start fighting in a new direction and then guess what? You change the game again. It tires them out quickly. When I'm smallmouth fishing I like to fish crayfish patterns which means (around here)I often hook into large carp unexpectedly. Sometimes, I swear, the side pressure game is the only way to save your fly. If you'd like to learn more about this subject find a copy of "The Founding Fish" by John McPhee. He actually has a chapter about just this subject. Don't buy it, go to the library and see if you can borrow it. If you can't find it, check my profile and email me. I'll send you my copy if you promise to send it back when you're done. God, I love fishing.